Van starts great when yuou give it gas it bogs down at low speed can down shift and it will pick up speed act like its starving for gas engine is 4.3

carb needs adjusting --float sticking or may need rebuild rebuild

Try a different carb.

Does the engine rev up when you press on the gas or bog down?
Do you smell a funny smell when the truck is running?

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Huh? Doesn't it start out from a stop in first gear? Flush what, what belts?

When you press the gas pedal all the way down, does the engine speed up quite a bit, or stay at a very low RPM?

Does the engine miss? When did you last do a tune up? How many miles on the van? How does it run once you have reached high speeds? Any other symptoms?

Not much information for us to go on.

check cat.converter for blockage

I would change fuel filter first, but may be fuel pump??

Any check engine light or codes? My first thought would be tps or possibly fuel filter. As car builds up pressure a clogged filter would cause your symptom.

Has Neon do same, I ran fuel at low level, on hot day, ran engine until it started to act up & threw a fuel pressure gauge on it. Was at approx 5 psi. Cold next morning, 48-50 psi. Always hot day about 30-40 miles into work in morning, o.k. Sit in hot sun all day & would happen 3-4 times on way home. Sit and let cool, 20 minutes or so & go again for a while. Cool day, no problem. Change pump I would.

The cause of the low compression could be a valve is not completly sealing or bad piston rings. Depending on weather you have blue smoke out the exaust. If not then I'm sure you have a valve that is not completly sealing. Not some thing to just let go, first try Z-Max. Z-max helps get rid of carbon deposits in the engine.

The relays that you hear clicking away are the problem Im sure. more than one occasion I have seen the relays go out and cause this problem.

The reason the lights dim and the blower slows is the reduction of voltage the alternator is puting out. When the other problem is fixed then this new one will dissappear.

Try cleaning the throttle position sensor like you said. If the contact is dirty it will not run right.

Please let me know if your problems presist.

Thanks, Charlie

i would check to see if your fuel pump is working properly maybe first try replacing the fuel filter and running a fuel treatment.